You’re only given a little spark of madness and if you lose that, you’re nothing,” the late Robin Williams says in the first trailer for HBO’s documentary, Robin Williams: Come Inside My Mind.

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The film, which premiered at Sundance, features rare footage, including scenes from the comedian’s standup appearances interspersed with photos. The new trailer traverses his public and private world, providing insight on the comedian’s life and career via his own words, alongside his friends, peers and family.

“He was really comfortable onstage,” Steve Martin says in the clip. “Offstage, I just felt he was holding himself together.” Meanwhile, Billy Crystal talks about the funny phone messages Williams would leave for him.

Williams’ son Zak reflects on his father’s insecurities. “My father didn’t always feel like he was succeeding,” he remarks. “But he was the most successful person I know.”

Williams also discusses his craft as well as his personal battles, including footage of him speaking candidly about his fears and his issues with drugs and alcohol. “Stand-up is survival,” he explains. “For me, that’s jazz – that’s what I have to do.”